North Korea has declared that it has the capability to detonate hydrogen bombs at high altitudes to launch electromagnetic pulse (EMP) attacks. The threat, which followed the North's sixth nuclear test on Sept. 3, demonstrates that Pyongyang will never hesitate to do whatever it can to threaten the United States and its allies. Its cunning and persistent attitude has once again stunned us.

In an EMP attack, a nuclear explosion is triggered at an altitude of anywhere between several kilometers and hundreds of kilometers above a target country, releasing strong electromagnetic waves to destroy information- and communications-related technology and other infrastructure indispensable for people's lives.

This was the first time that North Korea had mentioned the possibility of launching an EMP attack.

Experts say that an EMP attack at an altitude of several hundred meters would not cause direct damage to people or buildings, unlike the atomic bombings on Hiroshima and Nagasaki. However, an EMP attack would almost completely paralyze distribution, medical and transportation systems in a modern society where computer networks are highly developed. Moreover, it would take a year or more to completely restore such systems hit by an EMP attack, endangering numerous people's lives.

The platform that the U.S. Republican Party adopted last year expressed wariness toward North Korea's moves, warning that an EMP attack on the United States would threaten the lives of millions of people.

At the same time, however, observations were prevalent in the United States that North Korea's long-range missiles could not withstand the intense heat at the time of re-entry into the atmosphere.

In apparent response to this, North Korea mentioned an EMP attack that does not involve a missile's re-entry into the atmosphere, in a bid to escalate its intimidation of the United States.

EMP attacks are not a new threat to the international community. In the 1960s, the United States and the Soviet Union learned that nuclear tests conducted within the Earth's atmosphere adversely affected electric and electronic systems in extensive areas far away from the test sites.

This led to the adoption of the Partial Test Ban Treaty in 1963 which prohibited nuclear tests in the atmosphere, outer space and under water. The United States and the Soviet Union, which had experienced the risk of a nuclear war in the Cuban Missile Crisis the previous year, managed to put the brakes on the threat posed by nuclear arms, including electromagnetic waves generated by detonating such weapons of mass destruction.

Following the 9/11 terrorist attacks, the United States once again focused on the risk of EMP attacks. Later in that year, Washington set up a panel of specialists to work out countermeasures in each field, such as the financial sector and defense, and has since been reinforcing communications networks in the country to protect them from electromagnetic waves.

In comparison, Japan has lagged behind other countries in countermeasures against EMP attacks. The Defense Ministry has requested the allocation of 1.4 billion yen in funds for research on EMP bombs from the fiscal 2018 budget. Nevertheless, there are many issues Japan should consider in response to an EMP threat, including the safety of nuclear plants.

Japan should not be at the mercy of intimidation by North Korea, but needs to calmly work out and implement measures to protect the safety of its society from such a threat.